Project Summary The long term goal of this research is to understand how cholesterol gains access to intracellular compartments for utilization, storage and cellular regulation, via two glycoproteins: NPC1 and LAMP proteins. NPC1 is needed for the egress of endocytosed, LDL-derived cholesterol from lysosomes into the cytoplasm. LAMP proteins constitute the major glycoproteins that line the limiting membranes of lysosomes. The goal of this application is to study how these proteins may cooperate to transport cholesterol out of lysosomes, using biochemical and cell biological approaches. Experiments are proposed to investigate further, the cholesterol-dependent interaction between these proteins, and how they, and their interactions, may influence downstream activation of lysosome biogenesis. These experiments will provide important information regarding how cells may sense and signal the availability of cholesterol in lysosomes, and export cholesterol from lysosomes. This work has important implications for a number of disease states including cardiovascular disease, cancer, and neurological disorders.